A piping system for vessels, marine structures, or land based plants may be assembled as a modular unit from individual components such as flange pipes, fittings, and instruments that are prefabricated in the foundry or pipe manufacturing factory. Alternatively, it may be constructed of integral structures on which system elements are pre-equipped. However, even if these prefabricated system elements or pre-equipped structures are themselves built within strict manufacturing tolerance, their actual assembly on the site does not always consummate a perfect fit as a whole. Where one-sided deviations from standard dimension concentrate locally, there occurs a misalignment between the ends of already assembled pipes so that use of a straight pipe or a standard elbow is impossible to interconnect the pipe ends. In traditional practice, a normally double-bent pipe or coupler is specially manufactured, based on actual measurements made between the free ends of already assembled pipes at the very side of constructing a pipe system. The pipe thus manufactured is fitted between those free ends.
To manufacture the coupler in a shape congruous enough to be precisely fitted in its place, a suitable measuring apparatus is required which is used to determine the length of coupler segments and the relative angle between them and determine its relative position to the flange bolts of each assembled pipe to obtain necessary dimensional data for designing its shape. There have been proposed many such devices.
The published Japanese Patent application No. 50-110964 discloses a typical apparatus of this kind. This apparatus consists of a graduated rod, a pair of graduated arms rotatably slidably mounted at their one end on the rod, and a pair of flange plates also rotatably slidably jointed to the opposite ends of the arms, respectively. In practice, the apparatus is held in suspended position between the free flanged ends of already incorporated flange pipes in which a specially manufactured coupler is to be connected, with the flange plates secured to the flanged end, respectively. The angular and positional relation of each flange plate to the associated arm is measured to determine the relative orientation of the coupler to each flanged end of the already assembled pipes and the distance between each point of bend and the plane of the corresponding flanged end. In addition, the angle defined by relative rotation of each arm to the rod is gauged to determine the relative orientation of the central portion to each bent end in the remodeled pipe. Moreover, the distance between the points at which the axis of the rod is intersected by the axes of the arms is measured to represent the length between the points of bend. Thus, with this conventional measuring apparatus, the measurer must take reading at a total of nine points for a single coupler to be manufactured.
However, these prior art measuring apparatus pose various problems. First, since their structural designs are such that the rod extends to stand in the way of the arm rotating beyond the point defined by the longitudinal axis of the rod (about 180.degree. C.), some difficulty is encountered in handling and in properly framing the apparatus as required at the site of measurement. Secondly, since the measuring operation in itself requires human attendance directly at the very spot where the apparatus is installed, use at a high place or a restricted area or under poor lighting condition must expect considerable inconvenience, with a resultant high risk of making errors of reading. In addition, since the measurer has as many as nine points at which to take reading for a single coupler, as stated earlier, not only is enormous effort imposed on the measurer, but also complicated operations are involved in subsequent processing of measured data.